Generally, exercises can be grouped into aerobic exercises, and anaerobic exercises. An aerobic exercise is performed at a low to moderate level of intensity over a long period of time, and an anaerobic exercise is performed at a high level of intensity. Under a long duration of an anaerobic exercise, an exerciser may accumulate excessive lactate, which causes muscular fatigue.
To identify whether an exercise is aerobic or anaerobic, an anaerobic threshold (AT) is needed. The anaerobic threshold is the point at which the exercise changes from aerobic to anaerobic. The anaerobic threshold (also called the lactate threshold) is defined as the level of exercise intensity at which lactate produces faster than it can be metabolized, and the heart rate at this point is called the anaerobic threshold heart rate.
The anaerobic threshold heart rate varies depending on an individual's physical conditions. The anaerobic threshold heart rate is generally estimated through measurement of ventilation rate or blood lactate. However, such a measurement is implemented by bulky and expensive instruments or blood sampling and testing processes need to be performed many times, thus bringing much inconvenience.